I'm struggling over the concept of how I should be doing my collisions for best performance.

I'm making a 2D RPG-esque game.

Would I be better off making the entire background as a single image and implementing some invisible walls in C2 that are solid in it's place (for things like book casses, chairs, walls, tables), or would I be better off just making a bare-bones tile set and adding several sprites to a scene with collision?

I suppose the flat picture with invis walls would likely perform better, but I'm not sure how to approach it.